Computer systems are known where execution of an instruction is predicated on some value identified or addressed in the instruction. However, in these computer systems, the operation defined in the instruction is either carried out or not carried out.
Computer systems are also known which act on so-called packed operands. That is, each operand comprises a plurality of packed objects held in respective lanes of the operand. The degree of packing can vary and for 64 bit operands it is known to provide byte packing (eight objects per 64 bit operand), halfword packing (four objects per 64 bit operand) and word packing (two objects per 64 bit operand). With existing computer systems, when instructions defining such packed operands are predicated, the predication either causes the operation to be carried out on all of the operands or not to be carried out at all.